This invention relates to coated guidewire for use in catheters. The guidewires are coated with organosiloxane copolymer.
Guidewires for catheters have been coated with lubricants such as Teflon prior to winding the guidewire into a coiled form. When the coated wire has been tightly wound into an elongated coil, a safety core wire is inserted into the coil and is welded to the respective ends of the guidewire. The safety core wire generally takes the form of a cylindrical wire having a uniform main body which is smoothly tapered into a very flexible flattened tip so that one end of the guidewire exhibits the property of being rigid and the other end of the guidewire remains very flexible.
In inserting a catheter into the vascular system of a patient, the guidewire is initially inserted through a cannula into the vascular system, the cannula is removed, and the catheter is inserted over the guidewire. The catheter is then moved along the guidewire to the desired position within the vascular system and the guidewire is removed. Once the guidewire has been removed, the catheter is in condition for use.
Accordingly, the guidewire must be extremely flexible at the distal end so that the guidewire may be initially moved through the vascular system to a position where it is desired to insert the cannula. The proximal end of the guidewire should remain relatively rigid so that the position of the guidewire may be controlled upon insertion of the guidewire within the vascular system. It is, therefore, desirable that the guidewire have a flexible distal tip and a relatively stiff body portion. In addition, the guidewire should have a very smooth and lubricious outer surface.
Guidewires generally take the form of a tightly wound spring which is constructed of a very fine wire tightly wrapped to form a coil in which all of the turns contact adjacent turns. It is important that the guidewire surface be as smooth as possible so that the internal walls of the vascular system are not traumtized or damaged during movement of the guidewire through the vascular system.
As is apparent, any material introduced into the bloodstream has the potential of initiating blood clots. Since blood clots are an undesirable side effect of known angiographic guidewires, it is desirable to utilize materials which eliminate the probability of the formation of blood clots and include a surface which is as lubricious as possible thereby preventing trauma to the blood vessel.
One approach to preventing blood clot formation is the use of a guidewire surface which is coated with Teflon prior to winding to provide a relatively smooth antithrombogenic surface. Such a Teflon coated angiographic guidewire is disclosed in U.S. Pat. No. 4,003,369.
While Teflon coated guidewires provided a substantial improvement over previously developed guidewires, the guidewire of the present invention has with improved lubricity with reduced trauma to the blood vessel system.
As will be described in greater detail hereinafter, the guidewire of the present invention is coated with an organisiloxane copolymer to provide the enhanced lubricity with reduced trauma to a blood vessel system. Such a copolymer has been proposed for use as a coating for a fine cutting edge in U.S. Pat. No. 3,574,673. However, heretofore, such a copolymer has not been proposed as a coating for an angiographic guidewire.